Facebook today announced the Antivirus Marketplace, or just The AV Marketplace for short. The news is two-fold: the social network giant has partnered with Microsoft, McAfee, TrendMicro, Sophos, and Symantec to provide its users with access to full version antivirus software free for six months, and the five companies will also augment Facebook's URL blacklist system with their own URL blacklist databases.

First let's talk about the free software, since everyone likes free stuff. The AV Marketplace is aimed at the hundreds of millions of Facebook users who don't currently have security protection on their computer. Facebook lets you download licenses to full versions of antivirus software: Microsoft Security Essentials, McAfee Internet Security 2012, Norton AntiVirus, Sophos Anti-Virus for Mac Home Edition, and Trend Micro internet security for PCs and Macs. After six months, for the ones that aren't free forever, you'll have to pay up.

The marketplace is accessible from the Facebook Security Facebook Page, or via this direct link: on.fb.me/FBAVMarketplace. Facebook wouldn't say, but I'm assuming it will eventually expand its list of antivirus partners to offer further free alternatives for its users. The social networking giant says arming its users with antivirus software will "empower them to stay safe no matter where they are on the web."

At the same time, Facebook's over 901 million active users will now be protected by the combined intelligence blacklists of the security industry. Facebook's URL blacklist system, which already scans trillions of clicks per day, will now incorporate the malicious URL databases from these security companies.

This means that whenever you click a link on Facebook, it not only be checked against Facebook's blacklist, but also the blacklists provided by Microsoft, McAfee, TrendMicro, Sophos, and Symantec. For more information on how Facebook's URL blacklist system works, check out How Facebook protects users from malicious URLs.

Last but not least, Facebook also said these companies will be writing posts on Facebook Security to provide important security material to help Facebook users keep themselves, and their data, safe. To get these updates in your News Feed and Ticker, you'll need to Like the Facebook Page.

"Nothing is more important to us than the safety of the people who use Facebook, and the security of their data," a Facebook spokesperson said in a statement. "The Facebook Security Team has pioneered many innovative defense systems against viruses, spam and phishing attacks, as well as extensive automated enforcement mechanisms that quickly shut down malicious pages, accounts and apps. Truly effective security requires cooperation and we are excited about this partnership with many of the leaders in the security community to better help us defend against existing threats, anticipate new ones and arm people with the tools they need to protect themselves."